Another alternative is to organize processes in a tree topology. Byzcoin [1]} organizes processes in a binary tree where signatures (votes) are aggregated as they are relayed up the tree from the leaf nodes to the root, and the results are disseminated from the root to the leaves. While this design results in linear message complexity and has good load balancing properties, the failure of a single internal node may prevent termination. Byzcoin overcomes this difficulty by falling back to a clique topology (which has quadratic message complexity) when consensus fails.
